The present invention generally relates to vehicle brake systems, and more particularly relates to a pneumatic brake force booster with means for fastening the booster to a vehicle wall.
DE 32 04 549 A1 discloses a brake force booster of this general type. In this booster, a cylindrically deflected housing area which includes a stop in the area of a housing opening for the fastening means that is adjustable in an axially inward direction. Further, the stop which is configured as a nut extends with an annular projection which points axially outwards over the mentioned cylindrical area in such a fashion that an annular interspace for a sealing ring is formed. The sealing ring seals a slot between the nut and the housing due to radial compression. The sealing ring does not serve for sealing the thread between the fastening means and the nut. A sealing compound which is liquid in its original condition is used for this purpose and is applied to the thread or, after the assembly of the brake force booster, to the nut, and then hardens. The sealing compound simultaneously prevents xe2x80x98an inadvertent rotation of the adjustable stopxe2x80x99.) The sealing of the housing openings as well as the anti-rotation mechanism of the adjustable stop is capable of improvement. On the one hand, there is the requirement of providing a self-boosting sealing arrangement wherein an increased difference in pressure between the interior of the brake force booster and the environment achieves an enhanced sealing effect. It is not precluded in the brake force booster of the prior art that fatigue of the sealing ring will reduce the sealing effect.
Also, the assembly of the sealing ring is desired to be carried out as simply a possible and in a reproducible manner. In the arrangement according to the above-mentioned state of the art, there is the possibility of damaging the sealing ring due to sharp edges when the nut is unscrewed. Admittedly, for eliminating this problem, it is known in the art to arrange the sealing ring on a frontal end (on the housing side) of the nut. However, this measure does not reduce the total effort involved in sealing and, especially, the effort involved in applying the sealing compound.
An object of the present invention is to overcome the disadvantages described hereinabove and, in particular, to achieve a simple solution for sealing. Another object of the present invention includes providing a different anti-rotation mechanism for the adjustable stop.
It has been found that this object is achieved with the present invention in that the fastening means has a smooth sealing portion adjacent to the adjustment area of the adjustable stop, and in that the sealing means, by multilateral abutment on a conical abutment surface of the adjustable stop, on the smooth sealing portion and the associated housing portion, closes a slot between the fastening means and the adjustable stop and a slot between the fastening means and the housing part.
According to the present invention, there is no need for a housing portion that projects cylindrically in the direction of the stop as an abutment for a seal. The conical abutment surface for the sealing means minimizes damages in the assembly and, in addition, along with further characterizing features permits a three-sided abutment, i.e., on the housing part, on the fastening means, and on the stop. This measure permits closing both slots with only one component part so that the effort required for sealing is considerably reduced. It is furthermore favorable that the sealing means is automatically centered during the assembly. Finally, self-boosting of the sealing effect is achieved because at least part of the interspace for the sealing means is permanently subjected to vacuum so that the ambient air pressure which acts from outside presses the corresponding housing area of the housing part permanently in the direction of the sealing means in order to boost the sealing effect.
Further advantages of the present invention can be taken from the subclaims in connection with the description and the accompanying drawings.